1992 240SX : Cooling problem

[SIeeper]

I have a base model 1992 240SX and I'm currently experiencing some cooling problems. Here's the scenario:

I start up the car. Initially it is running cold and then after a few minutes of driving it heats up to normal operating temperature. Then, after a few more minutes of driving (nothing hard, 50 mph max city streets, a few stoplights) the temp gauge needle gets way up on the H. It stays up here for a few minutes and then returns back to normal temp. Once it goes back to good, it stays that way.

This led me to believe it was the thermostat. I replaced it and bled my cooling system correctly and the problem is still there. I don't think that my water pump is bad since I'm not seeing any coolant coming out of it. My radiator (stock unit) has been leaking slightly from the top where the end tank is crimped to the core ever since I've had the car (1.5 years). I make sure the coolant is full and the radiator isn't leaking any worse than before I had this problem. I don't think it's the radiator since it has been leaking the same as it always has but I am just now having the cooling problems.

Could it be my coolant temp sensor? I plan to clean the contacts of the CTS and see if that does anything. I'm missing my OEM lower cooling panel and the lower fan shroud, which I need to replace, but they were off the car last summer and I didn't have problems then.

I have done lots of searching on the forums too. Thanks for any help.

[rogoman]

What was your replacement thermostat, OEM or some aftermarket unit like a Stant. If it was an aftermarket unit, then you may end up with more problems; get rid of it and get a NEW OEM unit from a Nissan dealer.

[SIeeper]

It was an aftermarket unit from NAPA. When I got it they asked me if I wanted to change to get a 180F one instead (i have no clue why somebody would do that) but I stuck with the 170F like the FSM said.

[rogoman]

Don't fool around; get an OEM unit from Nissan.

The OEM unit specs are: valve opening temp - 170 Fmax valve lift - 194 F

[SIeeper]

Another question: The small hole in the body of the thermostat, does that always have to be on top? I don't recall reading in the FSM about a particular orientation, but after doing some searches people said it needs to be on top.

[rogoman]

Yes, the 'steam hole' must be on top.

[SIeeper]

Thanks for the help rogoman. While I'm at it I might as well replace my water pump and my radiator.

[SIeeper]

I still haven't gotten the new Nissan thermostat yet, but after reading a post I thought of another problem. Since my radiator leaks, could it be that if the coolant is low it will cause the CTS to read incorrectly? I'm going to check my ECU for a code 13 tonight.